Free TNT Equivalent Calculator

The TNT Equivalent Calculator offers a straightforward method for converting the mass of any explosive into its TNT equivalent weight, making explosive energy comparison easy and consistent. With this tool, you can quickly answer questions like "How many kilograms of C4 are needed to match the energy of one kilogram of TNT?"

To enable such comparisons, a universal reference was essential. TNT (trinitrotoluene) was chosen because its blast behavior closely mirrors that of most solid‑type explosives. The TNT equivalent is a key parameter in designing blast‑resistant structures, determining pressure loads during explosions, and converting energy between different settings.

TNT Equivalent Weight and TNT Factor

The core concept behind TNT equivalence is the ratio of the heat released when a substance detonates. One kilogram of TNT releases 4.184 MJ of energy upon detonation. For any explosive with a measured heat of detonation $H_{\text{exp}}$ (expressed in MJ/kg), the TNT factor is defined as:

$$\text{TNT Factor} = \frac{H_{\text{exp}}}{4.184}$$

If you have a mass $W_{\text{exp}}$ (in kg) of that explosive, the TNT equivalent weight $W_{\text{eq}}$ is computed as:

$$W_{\text{eq}} = W_{\text{exp}} \times \text{TNT Factor} = \frac{W_{\text{exp}} \times H_{\text{exp}}}{4.184}$$

All masses are in kilograms and energies in megajoules.

Common Explosives Reference Table

The table below lists a variety of explosives along with their detonation heats and corresponding TNT factors. You can use these values directly with the calculator.

Explosive	Heat of Detonation (MJ/kg)	TNT Factor
TNT	4.184	1.000
Baratole	2.209	0.528
Comp B	4.566	1.091
C4	4.715	1.127
HMX	4.821	1.152
Pentolite 50/50	4.545	1.086
PBX 9407	4.757	1.137
PETN	4.906	1.173
RDX	4.821	1.152
Tetryl	4.481	1.071
NQ	3.165	0.756
NG	4.715	1.127
Ammonium nitrate	1.757	0.420
ANFO	3.682	0.880
Natural gas	0.669	0.160
Ammonium picrate	4.058	0.970
HBX-3	4.268	1.020
Torpex	5.021	1.200
Tritonal	3.891	0.930
Amatol 80/20	4.895	1.170
Tetrytol 75/25	5.021	1.200

Note: Only about one‑third of the total chemical energy is released instantly during the detonation phase; the remainder is liberated at a slower rate as the explosive continues to burn, driven by its heat of combustion.

How to Use the Calculator

Determining the TNT equivalent of a given explosive involves a few simple steps:

1. Select or enter the explosive – Choose from the built‑in list of common explosives, or supply a custom heat of detonation if your substance isn’t listed.
2. The reference value is already set – The calculator assumes 4.184 MJ/kg for TNT, so you don’t need to enter it.
3. Specify the mass – Input the weight of your explosive (in kilograms).
4. Read the results – The tool displays both the TNT factor and the equivalent TNT weight (in kg).

Worked Example: 6.5 kg of C4

To see how this works in practice, consider 6.5 kg of C4.

• From the dropdown list, choose C4. The tool loads its heat of detonation: 4.715 MJ/kg.
• The TNT factor is automatically computed as $4.715 / 4.184 \approx 1.127$.
• Enter the mass: 6.5 kg.
• The TNT equivalent weight is therefore $6.5 \times 1.127 \approx 7.326$ kg of TNT.

So, 6.5 kilograms of C4 release roughly the same explosive energy as 7.33 kilograms of TNT. You can also reverse the calculation — if you know the desired TNT equivalent weight, simply divide by the factor to find the required mass of the chosen explosive.